808. ELEY, D. D., AND RIDEAL, E. K. Catalysis of the Parahydrogen Conversion by Tungsten. Proc. Roy. Soc. (London), vol. 178, A, 1941, pp. 429-451; Chem. Abs., vol. 36, 1942, p. 22.
The p-H2 conversion was measured on the surface of W as a function of the surface concentration of adsorbed O acting as a poison. The O decreases the fraction of the metal surface available for reaction and affects the reactivity of the neighboring chemisorbed hydrogen. Dipole-dipole interaction between the adsorbed atoms may be an important factor in this. A part of the O adsorbed on W can be removed at room temperature by reaction with H2. Films of CO, N2, and C2H4 also act as poisons, and it appears that the small conversion that takes place when they are present is due to the formation of a hydride surface on top of the film rather than on gaps in it. Constants for the reaction are calculated, including the temperature-independent factor for the zero order reaction. The reaction is considered in terms of the activated complex theory and is shown to be more in accordance with a conversion mechanism based upon an interchange between loosely adsorbed H2 molecules and chemisorbed H than with the original idea of the recombination of chemisorbed H2 atoms. The H2+D2 reaction has the same rate as the p-H2 conversion; hence tunneling in the potential barriers plays an unimportant part in this H2 reaction, even at –150°. The H2+D2 reaction has about the same activation energy as the parahydrogen conversion. This, measured at 1.3 mm., is 3,070 cal. The 2 reactions are kinetically identical and go through the same mechanism.
ELFSTROM, N. See abs. 1623.